1. Field of the Invention
The present invention relates generally to the field of producing oriented films and membranes on a substrate. More particularly, it concerns a method of producing oriented films and membranes by pulsed laser deposition followed by a hydrothermal treatment.
2. Description of Related Art
Thin films composed of molecular sieves have attracted interest because of their potential applications in areas such as separations, catalysis, and sensors. Microporous molecular sieves are attractive materials for membrane-based applications, in part, because of the selective adsorption properties imparted by their uniform pore structure. Microporous molecular sieves offer several advantages over dense inorganic or polymeric thin-film materials which include, for example, high selectivity due to uniform pore size, thermal stability, and facile diffusion. Of particular interest are crystalline films that are oriented in such a way that specific pores define the exposed surface. Preferred crystal orientation offers several advantages in optimizing the efficiencies of gas separations as well as catalytic processes.
A variety of strategies have been developed for the fabrication of continuous films. The deposition and growth of crystals from solution onto a substrate is the most common approach, but this generally results in isolated crystals that must be grown sufficiently large so as to merge and form a continuous film. This aspect can make the preparation of thin films a challenge especially in the nanometer range. Recent efforts in controlling reaction conditions and the use of nanometer-sized seed crystals have improved the quality of some synthesized films and in some cases led to growth of oriented films. For the most part, however, these advancements have been limited to small and medium pore size zeolites such as those with the MFI and LTA topologies.
Many applications proposed for mesoporous molecular sieves would benefit from the ability to fabricate these materials into thin films. Previous attempts to prepare films of the hexagonal one dimensional channel type mesoporous silica, however, have only yielded films in which the pores are oriented parallel to the air/solution or substrate/solution interface.
In one respect, the invention is a method of forming an oriented film on a substrate. A target including a phosphate is provided. Material is ablated from the target onto the substrate to form a film. The film is heated in a synthesis gel of the target to orient the film. In another respect, the invention is a film made by this method.
In other aspects, the target may include an aluminum phosphate, a silicon aluminum phosphate, or a metal aluminum phosphate. The target may include at least one of VPI-5, AlPO4-5, AlPO4-8, SAPO-5, SAPO-37, SAPO-42, MAPO-39, MAPO-5, MAPO-11, UCSB-6, UCSB-7, or a mixture thereof. The film may be heated with the film being positioned face down at an angle between about 0 degrees and about 60 degrees in a reactor, the angle being measured from a plane horizontal to the reactor. The method may also include adjusting a background pressure of the substrate to between about 150 mTorr and about 350 mTorr. The background pressure may include a background pressure of O2. The substrate may include a porous substrate. The substrate may include a zeolite crystal, glass, metal, metal oxide, or plastic. The method may also include separating liquids or gases with the film.
In another respect, the invention is a method of forming an oriented film on a substrate. A mesoporous target is provided. Material is ablated from the target onto the substrate to form a film, and the film is heated in a synthesis gel of the target to orient the film. In another respect, the invention is a film made by this method.
In other aspects, the target may include at least one of MCM-41, MCM-48, SBA-15, SBA-16, Nb-TMS-1, Ti-TMS-1, Ta-TMS-1, or a mixture thereof. The film may be heated with the film being positioned face down at an angle between about 0 degrees and about 60 degrees in a reactor, the angle being measured from a plane horizontal to the reactor. The method may also include adjusting a background pressure of the substrate to between about 150 mTorr and about 350 mTorr. The background pressure may include a background pressure of O2. The substrate may include a porous substrate. The substrate may include a zeolite crystal, glass, metal, metal oxide, or plastic. The method may also include separating liquids or gases with the film.
In another respect, the invention is a method of forming an oriented film on a substrate. A target including a zeolite other than UTD-1 is provided. Material is ablated from the target onto the substrate to form a film, and the film is heated in a synthesis gel of the target to orient the film. In another respect, the invention is a film made by this method.
In other aspects, the target may include at least one of ZSM-5, Beta, Mordenite, NaX, NaA, SSZ-33, SSZ-31, SSZ-42, MCM-22, or a mixture thereof. The film may be heated with the film being positioned face down at an angle between about 0 degrees and about 60 degrees in a reactor, the angle being measured from a plane horizontal to the reactor. The method may also include adjusting a background pressure of the substrate to between about 150 mTorr and about 350 mTorr. The background pressure comprises a background pressure of O2. The substrate may include a porous substrate. The substrate may include a zeolite crystal, glass, metal, metal oxide, or plastic. The method may also include separating liquids or gases with the film.
In another respect, the invention is a method of forming an oriented film on a substrate. A target including a zeolite other than UTD-1 , the target also including Cp*2Co+ or Cp2Fe, is provided. Pulsed laser radiation having an energy between about 70 mJ/pulse and about 200 mJ/pulse at a repetition rate of between about 1 Hz and about 50 Hz is directed to the target to create a plume. The substrate is heated. A pressure between about 150 mTorr and about 350 mTorr about the substrate is maintained. The substrate is placed in operative relation to the plume to deposit target material onto the substrate to form a film, and the film is heated in a synthesis gel of the target to form the oriented film.
In another respect, the invention is a method of forming an oriented phosphate film on a substrate. A target including a phosphate and CP*2Co+ or Cp2Fe, is provided. Pulsed laser radiation having an energy between about 70 mJ/pulse and about 200 mJ/pulse at a repetition rate of between about 1 Hz and about 50 Hz is directed to the target to create a plume. The substrate is heated. A pressure between about 150 mTorr and about 350 mTorr about the substrate is maintained. The substrate is placed in operative relation to the plume to deposit target material onto the substrate to form a film, and the film is heated in a synthesis gel of the target to form the oriented film.
In another respect, the invention is a method of forming an oriented mesoporous film on a substrate. A target including a mesoporous molecular sieve and CP*2Co+ or Cp2Fe, is provided. Pulsed laser radiation having an energy between about 70 mJ/pulse and about 200 mJ/pulse at a repetition rate of between about 1 Hz and about 50 Hz is directed to the target to create a plume. The substrate is heated. A pressure between about 150 mTorr and about 350 mTorr about the substrate is maintained. The substrate is placed in operative relation to the plume to deposit target material onto the substrate to form a film, and the film is heated in a synthesis gel of the target to form the oriented film.
In other aspects, the method may also include coupling a blank substrate adjacent the film prior to the heating the film. The method may also include inserting a spacer between the blank substrate and the film.